The Department of Molecular Microbiology and Immunology (MMI) of the Johns Hopkins Bloomberg School of Public Health conducts research and provides training in the basic biological disciplines on which an integrated approach to public health depends. Departmental programs in microbiology, immunology, and molecular and cell biology stress proficiency in the fundamentals of those fields. However, MMI is a unit of a school of public health and its training programs benefit from an orientation fundamentally different from that of traditional departments of microbiology, molecular biology, or cell biology. It is the conscious goal of all Departmental programs to produce graduates capable of identifying problems of global public health importance and is dedicated to bringing state-of-the-art science to bear on those problems. The present application is for continued support for a training program in the Molecular and Cellular Bases of Infectious Diseases that will allow eight predoctoral and three postdoctoral students to study molecular and cell biology as applied to infectious diseases. The predoctoral training program comprises both course work and research training supplemented with seminars, journal clubs, and a Department-wide Research Forum, and annual Retreat designed to foster interactions between laboratories with diverse interests. Course work usually completed within the first 2 years, includes required courses in molecular and cell biology, immunology, virology, bacteriology, parasitology, ecology, research ethics, and an introduction to the population-based perspective of public health. Trainees will complete course work credit requirements with electives providing depth in their field of interest and familiarity with other disciplines represented in the School, such as epidemiology, biostatistics, and international health. During the first year, trainees will also conduct brief research projects in three different laboratories in the Department. Upon completion of their course work, trainees will participate in Department and University-mandated written and oral qualifying examinations, and upon successful completion, will begin thesis research. Progress will be monitored by an advisory committee that will be chaired by the thesis preceptor. After completion of thesis research, each trainee will participate in a final thesis defense. The postdoctoral program is a structured program designed specifically to acquaint a selected group of physicians and scientists with the exciting opportunities available for fundamental research in public health-related fields. It will involve the close interaction of the trainee with a mentor in the conduct of a research project and the opportunity to take courses in areas of public health relevance. Participation in seminars, journal clubs, the Departmental retreat, and Research Forum will also be required.